The present invention relates to an integrated circuit detecting the characteristic of an external system, said integrated circuit comprising at least one output circuit means connected to an output terminal for controlling a plurality of various external systems capable to be connected to said terminal.
During the design and the construction of electronic systems it is often required to provide a same basic circuit, for example the integrated circuit of the system, for controlling various kind of external circuits, in order that the basic circuit be utilized for many different applications. It is then necessary to have means for distinguishing the different variants of external circuit and for indicating to the basic circuit what is the variant to be controlled.
Generally, such an indication is given by an electric connection on a particular input line. However, such a principle presents the following drawbacks:
it is in principle necessary to provide the basic circuit with a separate input terminal for each variant of external system to be controlled. This is particularly unfavourable if the basic circuit is an integrated circuit because of the price of the additional terminals and the prohibitive place taken by these terminals, PA1 it is necessary, in the course of the assembly, to provide a particular connection in accordance with the foreseen application of the device, PA1 there exists a risk of error in the establishment of this connection.
The published PCT application WO 80/00038 describes a device for monitoring the seven segments of a liquid crystal display which permits the automatic determination, by use of the capacitive behaviour of the display, of the faulty or short circuit segments. Such a device is very specific and it does not allow to control various kind of external circuits with a same basic internal circuit.
The document "ELECTRONICS, Vol. 47, no 8, Apr. 18, 1974, page 118", relates to a continuous monitor for seven-segments displays. It describes a circuit for automatic testing each segment of the seven-segment digital display at the rate of one segment every second. The device is also very specific and it applies only for incandescent or light-emitting-diode displays.